Semiconductor manufacturing processes enable manufacturing of MEMS (Micro-Electro-Mechanical Systems) devices comprising suspended structures that are able to operate as transducers (i.e., to convert the movement of the suspended structure, due to external forces, into electrical signals) or as actuators (i.e., to generate a movement of the suspended structure starting from an electrical control signal).
In particular, in some applications, the suspended structures have a small thickness as compared to their area and are defined as diaphragms. Further, manufacturing processes are known providing the diaphragm in a monolithic silicon substrate above a buried cavity.
For example, European patent EP 1577656 describes a pressure sensor of a capacitive type in which the diaphragm is formed by providing, in a body of monocrystalline silicon, deep trenches separated by silicon columns. Then an epitaxial growth is carried out in a deoxidizing environment for causing growth, above the silicon columns, of an epitaxial layer that closes the trenches at the top. This traps the gas present therein. A thermal annealing treatment is carried out that causes migration of the silicon atoms and formation of a buried cavity delimiting at the top a suspended diaphragm. In the same patent, fabrication of a pressure sensor of a piezoresistive type is also described, including piezoresistive elements arranged on the periphery of the suspended diaphragm.
Various techniques are further known for forming MEMS components that include magnetic layers. For example, US 2012/0024389 describes an integrated electromagnetic actuator comprising a passive element of ferromagnetic material carried by a diaphragm, which is suspended over a cavity and is able to undergo bending. A coil and a magnetic core co-operate with the passive element for causing deflection of the diaphragm in a controlled way and displacement of a fluid contained in the cavity under the diaphragm. The diaphragm is typically formed as an adhesive film deposited above the cavity.
Known devices may be improved in regards to effectiveness, dimensions, manufacturing costs, and applicability.